Fluorocyclopropane anesthetics

ABSTRACT

THE PROCESS OF INDUCING ANESTHESIA IN A MAMMAL WHICH COMPRISES ADMINSTERING TO SAID MAMMAL BY INHALATION AN EFFECTIVE QUANTITY FOR INDUCING ANSETHESIA OF A CYCLOPROPANE SELECTED FFROM THE GROUP CONSISTING OF 1CHLORO-1,2,2-TRIFLUOROCYCLOPROPANE, 1-BROMO-2,2-DIFFUOROCYCLOPROPANE AND 1,1-DIBROMO-2,2-DIFLUOROCYCLOPROPANE.

nited States Patent 1 3,839,589 FLUOROCYCLOPROPANE ANESTHETICS Gerald Joseph ONeill, Arlington, Charles William Simons, Bedford, and Charles A. Billings, Concord, gass, assignors to W. R. Grace & Co., Cambridge,

ass.. 1 1 v No Drawing. Continuation-impart of abandoned applications Ser. No. 259,086, June 2, 1972, and Ser. No. 370,264, June 15, 1973. This application Sept. 7, 1973, Ser. No. 395,303

Int. Cl. A61k 27/00 US. Cl. 424-352 4 Claims ABSTRACT OF THE DISCLOSURE The following fluorocyclopropanes have been found useful as general inhalation anesthetics: 1-chloro-l,2,2,- trifluorocyclopropane, 1-bromo-2,2-difluorocyclopropane and 1,1-dibromo-2,2-difiuorocyclopropane.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation of applications 259,086 filed on June 2, 1972 and 370,264 filed on June 15, 1973. Application 370,264 is in turn a division of 258,957 filed on June 2, 1972; it was filed to separate the anesthetic process invention from the chemical invention originally disclosed.

Applications S.N. 259,086 and 370,264 are now abandoned.

THE PRIOR ART Although a certain number of halogenated hydrocarbon compounds have joined the ranks of useful anesthetics in the recent past, little has been added to the understanding of the mode of action of chemical compounds in this physiological role, and the relationships of the differences between fairly closely similar compounds with either their toxic or therapeutic properties remain substantially unidentified. In view of this situation, the discovery of additional substances possessing a desirable combination of properties for anesthetic purposes still lies beyond the scope of routine expertise.

SUMMARY OF THE INVENTION It has now been discovered that l-chloro-1,2,2-trifluorocyclopropane, 1-bromo-2,Z-difluorocyclopropane and 1,1- dibromo-Z,2-difiuorocyclopropane possess high potency as general anesthetics when administered to inhalation anesthetic-susceptible organism.

DETAILED DESCRIPTION The compounds of this invention can be prepared by the reaction of an appropriate halocarbene with an olefin according to the method of RB. Sargent [J Org. Chem. 35 (3), 678-682 (1970)]. The carbene is generated in the presence of the olefin by the thermal decomposition of either the corresponding phenyl (trihalomethy1) mercury compound, according to the method of D. Seyferth et al. [J. Am. Chem. Soc. 87, 4259-70 (1965)], or hexattluoropropylene oxide, a compound that can be synthesized with relative ease [J. Org. Chem. 31 2312 (1966)]. The cyclization reaction may be illustrated as follows:

C-CC F, It should be noted that this method of synthesis does not always yield the compound desired possibly because, in some instances, either the cyclization does not take place or, if it does, the resulting cyclocompound is unstable at carbene generating temperatures.

7 3,839,589 Patented Oct. 1, 1974 .Ice

Example 1 To prepare the chlorocyclopropane compound of the present invention, 4-t-bu tylpyrocatechol, 1 part by weight, is placed in stainless steel autoclave. The autoclave is sealedjevacuated, and cooled to 78 C. l-chloro-lfiuoroethylene, 80.5 parts, and hexafiuoropropylene oxide, 40.3 parts, are then introduced into the apparatus. The systemis heated for 8 hours at 185 C. After cooling to room temperature, the contents of the autoclave are transferred to a 196 C. trap. Materials boiling below room temperature are allowed to escape and the residue is purified by preparative vapor chromatography. The product has a molecular weight of 130, a boiling point of 31 C. and a d, of 1.358 g./ml.

Example 2 To obtain the monobromocyclopropane compound, 4-tbutylpyrocatechol, 1 part by weight, is placed in a stainless steel autoclave. The autoclave is sealed, evacuated, and cooled to -78 C. l-vinyl bromide, 116.2 parts, and hexafluoropropylene oxide, 46.4 parts, are then introduced into the apparatus. The system is heated for 8 hours at 185 C. After cooling to room temperature, the contents of the autoclave are transferred to a l96 C. trap. Materials boiling below room temperature are allowed to escape and the residue is purified by preparative vapor chromatography. The product has a molecular weight of 157, a boiling point of 68 to 685 C. and a d of 1.725 g./ml.

Example 3 The dibromo compound can be prepared as follows: A stainless steel magnetic-drive packless autoclave is charged with phenyl (tribromomethyl)mercury, 30 parts by weight. The autoclave is sealed, evacuated, and benzene, 66 parts, is drawn in. The autoclave is then pressurized to 225 psi. with vinylidene fluoride, in this instance 43 parts by weight. The sealed autoclave is then heated to to C. for 24 hours. The reaction mixture is cooled to room temperature and the volatiles are vented to the atmosphere. The remaining liquid, which contains the cyclopropane, is first purified on an auto annular Teflon spinning band column followed by preparative vapor phase chromatography. The product has a molecular weight of 236, a boiling point of 1l0-111 C. and a d, of 2.147 g./ml.

Example 4 The physiological effects of the three fluorocyclopropanes were demonstrated as follows, using a standard test for evaluation of inhalation anesthetics similar to that described by Robbins [L Pharmacology and Experimental Therapeutics 86, 197 1946)].

Mice were exposed to the anesthetic for a period of 10 minutes in a rotating drum. Observations were then made of the pinch reflex, the corneal reflex and the return of the righting reflex. At least four graded doses were employed to determine the minimum concentration required to anesthetize 50% of the mice used (AC5o) and the minimum concentration required to kill 50% of the mice (LC The anesthetic index (AI) was then calculated from these minimum concentrations. The results of these tests are summarized in the following table.

ANESTHETIC PROPERTIES When two figures are given, the actual value of the anesthetic index ies between these two figures.

For comparison, keeping in mind that otherdifi'erences in properties also exist, it may be considered that the widely used 1,1,1-trifiuoro 2-bromo-2-chloroethane (halothane) showed an anesthetic index of about 3.2 when tested under the same conditions.

What is claimed is:

1. The process of inducing anesthesia in a mammal which comprises administering to said mammal by inhalation an effective quantity for inducing anesthesia of a cyclopropane selected from the group consisting of 1- chloro-1,2,2-trifluorocyclopropane, l-bromo-2,2-difluorocyclopropane and 1,l-dibromo-2,2-difiuorocyclopropane.

2. The process of Claim 1 wherein the cyclopropane used is l-chloro-l,2,Z-trifluorocyclopropane.

' 3. Thetprocess of Claim 2 wherein the cyclopropane used is 1-bromo-2,2-difluorocyclopropane.

4. The process of Claim 1 wherein the cyclopropane used is 1,1-dibromo-2,Z-difluorocyclopropane.

References Cited 7 UNITED STATES PATENTS 3,349,136 10/1967 Boudakian 260--648 OTHER REFERENCES Larsen, Fluorine Chemistry Review, vol. 3, 1969, page JEROME D. GOLDBERG, Primary Examiner 

